interface Com{
	int add(int a,int b);
  }
abstract class A {
abstract int add(int a,int b);
}
class B extends A implements Com{
	public int add(int a,int b){
		return a+b;
  }
}
public class ceshi6_2 {
		public static void main(String args[]){
			B b=new B();
			Com com=b;
			System.out.println(com.add(12,6));
			A a=b;
			System.out.println(a.add(10,5));
  }
}